MAD Wurks Carbon Split Wide Rear Topdeck 2mm Schumacher Mi9 (1)

MAD Wurks Carbon Split Wide Rear Topdeck 2mm Schumacher Mi9 (1)

To add additional flex to suit your needs, you can cut one or multiple bridges out.
You also can cut from the front slot into the adjoining screw hole. This allows much more torsional twist.  

Adding flex allows the rear of the car to roll more and better wrap the corner.  
Adding too much flex can sacrifice rear end stability.

Starting recommendation on top decks is to run them as they come for most surfaces and conditions.

For the 2mm top decks, use the 2mm dowel bushing (u7783).